Abstract

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A new dicoumarinyl ether, 3-hydroxy-6-methoxy-7,7'-dicoumarinyl ether (1), was isolated from the roots of Stellera chamaejasme L, together with the known compound umbelliferone (2). Their structures were determined on the basis of spectroscopic techniques, including IR, NMR, and HR-ESI-MS.

1. Introduction

Stellera chamaejasme L. (Ruixianglangdu in Chinese, family Thymelaeaceae), has been used in China as an important traditional medicine for the treatment of scabies, tinea, stubborn skin ulcers, chronic tracheitis, cancer, and tuberculosis [1,2]. Previous phytochemical studies of S. chamaejasme showed the presence of groups of biflavonoids, diterpenes, lignans, and coumarins [3,4,5,6,7,8,9,10,11,12]. In our continuous studies on the chemical constituents of S.chamaejasme, a new bicoumarin, 3-hydroxy-6-methoxy-7,7'-dicoumarinyl ether (1, Figure 1) was isolated, together with the known coumarin umbelliferone (2). Here, we report the isolation and structure elucidation of the new compound.

The other unit was deduced to be a 3-hydroxy-6-methoxy-7-substituted- coumarin as follows: H-4 (δH 7.80) and H-5 (δH 7.24) showed a correlation in the NOESY experiment. Accordingly, cross-peaks between H-4 and C-5 (δC 109.9) and between H-5 and C-4 (δC 131.5) were evident in the HMBC experiment (Table 1). The correlation between the methoxy protons (δH 3.92) and H-5 in the NOESY spectrum indicated that the methoxy group was attached to C-6 (δC 146.6), which was further supported by the long-range correlation between the methoxy protons and C-6 in the HMBC spectrum. Compared with the known compound daphnoretin that was isolated from the same plant [13], the resonance of H-8' in 1 was shifted downfield by 0.22 ppm, and the H-8 one shifted upfield by 0.25 ppm, indicating that the two coumarin moieties were connected at C-7 and C-7' via an oxygen bridge, which was further supported by ESIMS/MS experiment of 1. The daughter ion peaks at m/z 206 and m/z 144 were derived from fission of the C-7'−O bond. Therefore, compound 1 was elucidated as 3-hydroxy-6-methoxy-7,7'-dicoumarinyl ether and named neodaphnoretin. The known compound was identified as umbelliferone (2) by comparison of its 1H- and 13C-NMR and MS data with published data.

3.2. Plant Material

The roots of S.chamaejasme were collected in Kunming, Yunnan Province, China, in October, 2010. The plant was identified by Le Cai (Yunnan University). A voucher specimen (LJ-RXLD1008) was deposited with the Zhejiang University City College.

3.3. Extraction and Isolation

Air-dried powdered roots (3.0 kg) of S. chamaejasme were extracted exhaustively with 95% aq. EtOH (2 L) at r.t. for four times (7 days for each time). After concentration in vacuo, a crude extract (360 g) was obtained, which was suspended in H2O (1 L), and the suspension was extracted three times successively with petroleum ether, EtOAc and BuOH (1 L). The EtOAc fraction (160 g) was subjected to column chromatography (CC) with a PE/EtOAc gradient system of increasing polarity (9:1, 8:2, 7:3, 6:4, 5:5) as eluent to give six fractions (Fr. 1–6). Fr. 3 was rechromatographed on a SiO2 column with CHCl3/MeOH (98:2→95:5) to give compounds 1 (34 mg) and 2 (23 mg).

Supplementary Materials

Acknowledgements

This work was supported by National Science Foundation of China under Grant [No. 81302668]; Zhejiang Provincial Natural Science Foundation of China under Grant [LQ12H30003]; and Hangzhou Science and Technology Information Institute of China under Grant [20120633B31].

Author Contributions

Xiang-Rong Li and Jie Li organized the study. Qian Shen, and Li-Ting Chen carried out the extraction and isolation. Jie Li and Chen-Hao Bao interpreted the results and helped write the manuscript.